early 14c. (diggen), of uncertain origin, perhaps related to dike and ditch, either via Old French diguer (ultimately from a Germanic source), or directly from an unrecorded Old English word. Native words were deolfan (see delve), grafan (see grave (v.)).

Slang sense of "understand" first recorded 1934 in African-American vernacular, probably based on the notion of "excavate." A slightly varied sense of "appreciate" emerged 1939. Strong past participle dug appeared 16c., but is not etymological. Related: Digging.